Smalling played the full 90 minutes as Manchester United beat West Brom 2-1 at the Hawthorns yesterday, taking over the captain's armband when Antonio Valencia was forced off through injury.

Last week, Mourinho confirmed Eric Bailly could be out for up to three months due to injury on an ankle injury.

Which means Smalling could be set for an extended period in the side with a mounting fixture list over the festive period.

The England defender began the season on the bench as Phil Jones and Bailly were Mourinho’s first choice but has worked his way back into the team.

And BBC Sport pundit Garth Crooks believes Smalling could become a key player for Mourinho.

He said: “Manchester United's win at West Brom wasn't an easy watch for me, in fact I found much of the game rather boring. 

“However, what I did find interesting was the captain's armband slowly finding its way to Chris Smalling. 

“In the absence of Antonio Valencia, who left this dull affair with a hamstring injury, I can't think of a more likeable or committed player to give the armband to. 

“All credit to manager Jose Mourinho - he does like to give the armband to those who don't crave the limelight.

“The Christmas period is going to be very demanding, and Smalling is the sort of player who will compete and lead by example. 

“No Eric Bailly (for at least a couple of months) or Daley Blind means United can't afford many more injuries or suspensions to their top defenders. So having Smalling around for so long has proved to be of real value. 

“He may not be the most gifted centre-back at the club, but he is certainly Mr Dependable.”